The present invention relates to a control system for a shock absorber device used in a suspension of an automobile, and more particularly relates to such a control system which controls a shock absorber which can be set to three different levels of damping effectiveness.
The present patent application has been at least partially prepared from material which has been included in Japanese Patent Application No. Sho 59-172146 (1984), which was invented by the same inventors as the present patent application, and the present patent application hereby incorporates the test of that Japanese Patent Application and the claim or claims and the drawings thereof into this specification by reference; a copy is appended to this specification.
The suspension of a vehicle such as an automobile typically incorporates at least one, and usually a plurality, of shock absorber devices, in order to provide damping action for the movement of the vehicle body with respect to the wheels thereof. Now, the amount of damping effect of such a shock absorber is preferred to be relatively low in order to provide good and comfortable vehicle ridability, but paradoxically is preferred to be relatively high in order to provide good and stable vehicle steering characteristics and turning characteristics such as anti roll, as well as good acceleration and braking characteristics such as anti squat and anti dive and anti starting squat and anti starting tail lift.
For this reason, there have been developed various types of shock absorber devices which have variable damping effectiveness. In the utilization of such a shock absorber for the suspension system of an automobile a control system therefor is provided which controls the damping effectiveness of the shock absorber, and varies it in accordance with various parameters of the vehicle relating to its operational conditions. Such systems are disclosed in Japanese Utility Model Laying Open Publication No. Showa 56-147107 (1981), Japanese Patent Laying Open Publication Ser. No. Showa 58-25708 (1983) relating to an application by an applicant the same as the applicant of the Japanese Patent Application of which priority is being claimed in this present patent application, Japanese Patent Laying Open Publication Ser. No. Showa 58-30541 (1983), Japanese Patent Laying Open Publication Ser. No. Showa 58-30542 (1983), Japanese Patent Laying Open Publication Sho 58-30818 (1983), Japanese Patent Laying Open Publication Ser. No. Showa 58-167210 (1983), and Japanese Patent Application Ser. No. Showa 59-4157 (1984), none of which are intended hereby to be admitted as prior art to the present patent application except to the extent otherwise required by law.
Such a shock absorber device is typically adjustable with regard to its damping effectiveness either to two discrete conditions, a first condition in which it provides a lower value of damping effectiveness and a second condition in which it provides a higher value of damping effectiveness, or to three discrete conditions, a first condition in which it proivdes a minimum value of damping effectiveness, a second condition in which it provides a medium value of damping effectiveness, or a third condition in which it provides a maximum value of damping effectiveness. In a typical control system for such a shock absorber device, the action is typically such that, either manually according to the preference of the vehicle operator or automatically according to the operational conditions of the vehicle, the shock absorber device is switched between its various conditions to provide varying damping effectiveness. For example the shock absorber device control system in the 1983 model Toyota Soarer GT automobile, which is manufactured by the applicant of the Japanese Patent Application of which priority is being claimed in this present patent application, can be manually set by the vehicle operator operating a mode select switch provided within the passenger compartment to any one of a "normal mode", a "sport mode", and an "auto mode". In the "normal mode" the damping effectivenesses of the shock absorber devices of the suspension of the vehicle are set to be constant at a relatively small value; in the "sport mode" said damping effectivenesses of said shock absorber devices are set to be constant at a relatively large value; and in the "auto mode" said damping effectivenesses of said shock absorber devices are switched between said relatively small value and said relatively large value according to signals output from various detecting means such as sensors and switches which detect operational parameters of the vehicle. In this way, it is possible to keep the shock absorbers of the suspension of the vehicle generally operating with sufficiently low damping effectiveness to provide good vehicle ridability, while at the same time when necessary altering the suspension characteristics of the vehicle so as to prevent such undesirable operational problems as vehicle body roll when the vehicle is turning a corner at speed, vehicle squat when the vehicle is being accelerated sharply, vehicle nose dive when the vehicle is being sharply braked, and vehicle starting squat when the vehicle is being accelerated away forward from rest as well as vehicle starting tail lift when the vehicle is being accelerated away backward from rest.
This type of system is effective, but suffers from the problem that in the manual or driver controlled mode the damping effectivenesses of the shock absorber devices can be set to the largest available value, i.e. to the hardest setting. This means that there is a risk that the case may arise wherein, for example due to improper or injudicious actuation of the system by the vehicle driver, the shock absorber devices are set to high damping effectivenesses which are harder than necessary, and the vehicle ridability may thereby be deteriorated. This means that operational comfort may be bad if, for example, the driver erroneously makes an operational mode selection which is inappropriate for the particular vehicle operational circumstances, or the driver is unaccustomed to the operation of the mode select switch and neglects its use, or the driver wrongly operates the mode select switch.